International Journal of Prosthodontics最新文献

Purpose: The purpose of this study was to compare soft tissue volumetric changes on buccal aspect and pink aesthetics score in immediate implant placement by socket shield and conventional technique.

Material and methods: This parallel-arm, randomized controlled trial included 22 participants requiring replacement of single maxillary incisor by immediate implant placement. Immediate implants were placed with socket shield technique (SST) and conventional technique (CT) in respective two groups after randomization. All implants were immediately loaded by immediate loading protocol. Definitive crowns were placed 6 months after implant placement. Scans of casts were recorded by using a digital white light scanner before implant placement and at the end of 12 months. Volumetric soft tissue changes on the buccal aspect was assessed by the superimposition of scanned cast. Esthetic evaluation of soft tissue was done by using pink esthetic score (PES) before implant placement, 6 months, and 12 months after implant placement. Statistical analysis of the data was performed using statistical software (Stata 16.0; Stata Corp LLC).

Results: The mean soft tissue volumetric change on the buccal aspect at the end of 12 months in the SST group was -0.1520 ±0.86 mm, and in the CT group was -0.643 ±0.35 mm and the difference was statistically significant (P=.001). Higher PES was observed in the SST group when compared to the CT group at all time intervals. The difference was statistically significant at 6 months (P=.001) and 12 months (P=.007).

Conclusions: The results of the study show less volumetric change on the buccal aspect and higher PES in SST when compared to CT. Int J Prosthodont 2023. doi: 10.11607/ijp.8063.

Purpose: Implant abutment design may influence the predisposition of peri-implant sites to develop peri-implant inflammation, especially peri-implantitis. Therefore, the objectives of the current study were to examine the influence of (1) abutment emergence angle and, (2) abutment height on marginal periimplant bone stability in patients not considered susceptible to peri-implantitis. Furthermore, it was analyzed (3) whether Ti-Base abutments lead to wider abutment emergence angles as compared to onepiece abutments.

Materials and methods: 48 abutments (i.e., 24 Ti-base- and 24 one-piece abutments in 24 patients) have been at abutment installation, after one year, and thereafter on a yearly basis for up to five years. Clinical and radiographic outcome variables were assessed.

Results: With regard to peri-implant marginal bone stability, (1) only moderately negative, albeit significant, correlations were found on the mesial sides of the one-piece abutments after 4 and 5 years for an abutment emergence angle >30° and no statistically significant negative correlations were found between a distance of less than or equal to versus more than 1.5 mm between the restoration margin and the crestal peri-implant bone level, neither for Ti-Base nor for one-piece abutments. Furthermore, (3) abutments bonded to Ti-bases are not associated with larger emergence angles than one-piece abutments.

Conclusion: For patients at low risk of developing peri-implantitis it can be concluded, that neither (1) a larger abutment emergence angle (>30°) nor (2) a distance of less than or equal to 1.5 mm between the restoration margin and the crestal peri-implant bone level are per se associated with marginal periimplant bone loss. Furthermore, (3) abutments bonded to Ti-bases are not as such associated with wider emergence angles than one-piece abutments. Int J Prosthodont 2023. doi: 10.11607/ijp.8138.

Purpose: Comparing the static and dynamic occlusion of all-ceramic single crowns designed by mechanical and virtual articulators, we evaluated the accuracy of occlusal contacts of prostheses designed by virtual articulators and the feasibility of clinical application of CADCAM virtual articulators.

Materials and methods: Nine subjects with an average age of 27 who needed crown repair were recruited. After preparation of the all-ceramic crown, two zirconia crowns were designed and fabricated through digital procedures and traditional methods. The intraoral scanner, Geomagic software and T-scan analyzer were used to analyze the occlusal contact points, areas, and the occlusal force percentage peak before the treatment and after the two crowns were temporarily fixed.

Results: There was a significant difference in the number of occlusal contact points and areas between the mechanical group and control group (preoperation group), but there was no obvious difference between the virtual group and control group. The occlusal contact overlapping areas of the virtual-control group were significantly larger than those of the mechanical-control group. The occlusal force percentage peak of the tested teeth was slightly larger in the mechanical group than in the virtual group.

Conclusion: The posterior single crown designed by a virtual articulator can restore the intercuspal occlusal better than by a mechanical articulator and produce less dynamic occlusal interference. This finding suggests that virtual articulators can provide guidance for the design and adjustment of the occlusal surface of posterior single crown prostheses. Int J Prosthodont 2023. doi: 10.11607/ijp.8298.

Purpose: To study the degree of accuracy in gingival colour matching of undergraduate students using a computer application.

Material and methods: Seventy-six undergraduate dental students were evaluated in gingival shade selection using an in-house developed computer application. Fifteen intraoral gingival photographs and 21 pink gingival colour porcelain samples were used. The environmental conditions were standardised, and no time limit was set for answering in the computer application.

Results: Fourteen gingival colour samples (66.6%) were not useful to represent the studied gingival shades. Not all natural gingival colours studied were represented within the 50.50% acceptability limits of the pink samples. There were no statistically significant differences between males and females in terms of "hit" percentages. The highest correlation coefficient (in absolute value) was for the L*-coordinate (the darker the gingiva in the picture, the higher the hit rate for choosing the "ideal" shade tab); however, none of the linear correlation coefficients were statistically significant.

Conclusions: Not all colours provided in the pink ceramic system were useful for subjective gingival selection. There were no statistically significant differences between male and female dental students in gingival colour perception. The L* coordinate was the only one that influenced the correct perception of gingival colour by dental students, and it does so more in women than in men.

Two clinical cases involving the fracture of a natural tooth and of a ceramic crown were presented and discussed based on fractography principles. In the first case, a patient reported intense pain in a sound third molar, where a longitudinal fracture was identified, and the tooth was extracted. In the second case, a posterior rehabilitation using a LS (lithium-silicate) ceramic crown was carried out and after one year, the patient returned with a fractured piece of the crown. Both were analyzed under microscopy, to identify the origins of fractures and their causes. The fractures were critically analyzed so that relevant information could be generated from the laboratory to clinic.

Purpose: The aim of the present study was to generate data on the long-term survival of metal-ceramic resin-bonded fixed partial dentures.

Material and methods: Eighty-nine participants, received 94 RBFPDs, 5 (n women = 1; n men = 4) received 2 RBFPDs each. All RBFPDs were fabricated as two-retainer end-abutment metal-ceramic restorations. Clinical follow-ups were performed 6 weeks after cementation and annually thereafter. The mean observation time was 7.5 years. Cox regression was performed to test the effects of the variables sex, location, jaw, design, use of rubber dam, and adhesive luting system Survival and success were calculated by using Kaplan-Meier curves. As a secondary objective, patient and dentist satisfaction with the esthetics and function of the RBFPDs was evaluated. The significance level was set at α = .05 for all calculations.

Results: Estimated Kaplan-Meier failure-free survival was 97.5% (standard error [SE] 1.7) after 5 years and 83.3% (SE 5.3) after 10 years. Calculated intervention-free survival (success) was 90.1% (SE 3.4) after 5 years and 65.5% (SE 6.7) after 10 years. Debonding-free survival was 92.6% (SE 2.9) after 5 years and 80.6% (SE 5.4) after 10 years. Cox regression revealed none of the four tested variables had a significant effect on the incidence of complications in RBFPDs. Patient and dentist satisfaction with RBFPD esthetics and function was consistently high throughout the observation period.

Conclusions: Within the limitations of an observational study, RBFPDs achieved clinically successful outcomes over a mean observational period of 7.5 years.

Purpose: To evaluate the marginal integrity of three inlay-retained fixed dental prosthesis (IRFDP) designs fabricated using monolithic zirconia.

Materials and methods: Thirty inlay-retained fixed dental prostheses were fabricated using a 4-YTZP monolithic zirconia, and divided randomly into 3 groups according to the cavity design. Group ID2 and ID1.5 received an inlay cavity preparation which includes a proximal box and an occlusal extension with a depth of 2 mm or 1.5 mm respectively. Group PB received a proximal box cavity preparation without an occlusal extension. The restorations were fabricated and cemented using a dual cure resin cement (Panava V5) and subjected to an equivalent of 5 years of ageing. The specimens were evaluated under a SEM to measure marginal continuity before and after the ageing process.

Results: During the whole 5-year ageing process, no specimens showed signs of cracking,fracture or loss of retention in any of the restorations. In the SEM analysis, most of the marginal defects observed in the restorations were areas of micro-gaps at the TC (tooth/cement interface) or ZC (zirconia/cement interface) resulting in loss of adaptation. There was a significant difference between the groups after the ageing process at both the TC (F=4.762, p<.05) and ZC (F=6.975, p<.05), with group ID2 presenting the best performance. There was a significant difference between TC and ZC in all groups (p<.05) with ZC presenting more gaps in all groups.

Conclusion: Inlay cavity design including a proximal box and an occlusal extension exhibited better marginal stability than a proximal box without occlusal extension.

Purpose: To evaluate relevant material properties (flexural strength (σf), elastic modulus (E), water sorption (Wsp) and solubility (Wsl), and biocompatibility) of a 3D-printed resin (3D) and a heat cured acrylic resin (AR-control) used for complete denture manufacturing, testing the hypothesis that constructs from both materials would present acceptable material properties for clinical use.

Materials and methods: The σf, E, Wsp and Wsl were evaluated according to the ISO 20795-1:2013 standard, and the biocompatibility was evaluated using 3-4,5-dimethyl-thiazol-2-yl-2.5-diphenyltetrazolium bromide (MTT) and sulforhodamine B (SRB) assays. Disk-shaped specimens were fabricated and used for Wsp (n = 5), Wsl (n = 5), and biocompatibility (n = 3). Bar-shaped specimens (n = 30) were fabricated and stored in 37⁰ C distilled water for 48 hours and 6 months before flexural testing in a universal testing machine with constant displacement rate (5 ± 1 mm/min) until fracture. Data from σf, E, Wsp, Wsl and biocompatibility were statistically analyzed using Student t test (α= 0.05), Weibull analysis was also used for σf and E data.

Results: Significant differences between the two polymers were found for the evaluated material properties. Water storage for 6 months did not affect the flexural strength of 3D. Yet, the additive manufactured polymer showed inadequate flexural strength and water solubility values.

Conclusion: Despite adequate biocompatibility and strength stability after 6 months of water storage, the additive manufactured polymer recommended for complete denture needs further development to improve the remaining material properties evaluated in this study.

Purpose: To assess two types of abutment materials routinely used in daily prac-tice-direct polymethyl methacrylate (PMMA) and a zirconia-on-Ti-base abut-ment-and their effects on peri-implant soft tissues and bone remodeling in a mini-pig model.

Materials and methods: A total of 40 implants were placed in five mini-pigs in a single-stage surgery. Four different types of abutment materials (n = 10 per group) were used: (1) titanium (control); (2) zirconia (control); (3) PMMA (test 1); and (4) Ti-base (zirconia bonded to a titanium framework; test 2). After 3 months of healing, the samples were collected and subjected to nondecalcified histology. The soft tissue dimensions (sulcus, junctional epithelium, and connective tissue attach-ment) were assessed on each abutment mesially and distally, and the distance from the implant margin to the first bone-to-implant contact (BIC) was measured.

Results: No statistically significant differences were found among the four groups regarding soft tissue dimensions (P = .21), and a long junctional epithelium (mean: 4.1 mm) and a short connective tissue attachment (mean: 0.3 mm) were found in the majority of abutments. In some samples, the junctional epithelium extended all the way to the bone level. The measured peri-implant bone remodeling was similar in all four groups (P = .25).

Conclusion: The present findings indicate that both di-rect PMMA and zirconia-on-Ti-base abutments seem to allow soft tissue integration similar to that of titanium and zirconia abutments. However, clinical studies are war-ranted to either confirm or refute the observed findings and to further investigate the influence of different materials on mucointegration.